Approximately one in seven couples has difficulty conceiving. Infertility may be due to a single cause in either partner, or a combination of factors (e.g., genetic factors, diseases, or environmental factors) that may prevent a pregnancy from occurring or continuing. Every woman will become infertile in her lifetime due to menopause. On average, egg quality and number begins to decline precipitously at 35. However, a number of women are fertile well into their 40's, while some women experience that decline much earlier in life. Although advanced maternal age (35 and above) is generally associated with poorer fertility outcomes, there is no way of diagnosing egg quality issues in younger women or knowing when a particular woman will start to experience decline in her egg quality or reserve. When a woman seeks medical assistance for difficulty conceiving, she and her partner are advised to undergo a number of diagnostic procedures to ascertain potential causes. Throughout the process, the couple's main question is whether that treatment will result in a baby.
Predicting a couple's probability of achieving a pregnancy that results in a live birth is difficult, and most statistical approaches do not provide an accurate result, generally over-estimating the couple's probability of achieving such a pregnancy. That problem is illustrated with the very common technology of in vitro fertilization (IVF), a process in which egg cells are fertilized outside a woman's womb and then implanted into the womb. Generally, about 52% of couples undergoing IVF do not achieve a pregnancy after a first cycle of treatment, and about 59% of couples undergoing IVF do not achieve a live birth after a first cycle of treatment (“2009 Clinic Summary Report”, Society for Reproductive Medicine). Accordingly, many couples will undergo at least one subsequent cycle of IVF, and a percentage of those couples will not achieve a pregnancy or live birth even after numerous IVF cycles.
In IVF, the statistic typically reported to couples is outcome per cycle according to maternal age (cross-sectional reporting). For example, a physician may tell a couple in which the woman is under 35 that they have a 30% to 35% probability of achieving a live birth using IVF, meaning that for each cycle of IVF started, there is a 30% to 35% probability that a live birth will be achieved. That statistic is not accurate because it does not consider the potential need for multiple IVF cycles and the likely difference in success between a first-time patient and one who did not become pregnant in previous attempts. Thus, using this cross-section reporting approach, a physician overestimates a couple's probability of achieving a pregnancy that results in a live birth from IVF.